A long-term research plan is proposed for the study of the mechanisms and social consequences of territorial behavior. The primary species to be studied is the Mongolian gerbil (Meriones unguiculatus), although comparative studies with other species of the same genus and the hamster, rabbit and marmoset monkey are anticipated. Our project represents a multifaceted approach to a problem area, territoriality, of importance to a host of species including man. While the emphasis is on behavioral aspects of the behavior, our investigations include the determination of genetic, neural and hormonal control mechanisms. We intend to interrelate mechanisms and put them in the context of evolution and adaptation. In total we hope to be able to specify and manipulate the pertinent natural control variables regulating population growth and social interactions in territorial species.